Did you get confirmation from service on that rejection ? Just in case it was some new shapie who
rejected a bunch of orders because s/he lacks the experience. (Seems odd to tighten the rules
for jewelry in the midst of the holiday shopping without advance warning to affected designers)

The rejections, three so far in the space of 5 days, came from Shapeways Production Partner via Shapeways Customer Service team. Apparently the model has been causing some hassle for some time, but it was only last Friday (7th) that I was first notified.

A snippet from the emails that have being going back & forth.

Quote:

I understand Paul's frustration on this one. I spoke to production prior to
the rejections and they have been having serious issues with this model for
quite some time now, this model always needs a lot of hand made support
stems to make sure it doesn't fail in printing or casting, and even then it
can still fail. The reason for this is that very long round wire that is
totally unsupported appart from both ends. The wax that we use to print our
models is very very fragile and it is very difficult to not break this
model. That's is why production rejected this model and they rejected it
after trying it first, that is why you see other versions still in
production. I'll see if we need to reject these models as well.

I've also asked what the recommended wire thickness should be to get the model printed first time every time, but alas, no response as yet and even if a response is forthcoming it will still be too late for those Christmas orders

My take on this is that I need to see failed pieces so that I can design around any problems. Having the machine operators repeatedly rebuilding failed pieces seem a waste of time and effort when the solution is likely to take a few minutes work on the original drawing.

Being able to see your mistakes is the best way of learning how not to design.

Bill is absolutely correct - seeing a failure is extraordinarily helpful to help avoid future failures. I recently had several copies of http://shpws.me/lnj8 delivered to a customer broken. The point of failure got past me, the reviewer, and the print cleaner... but the reason for the failure was obvious to me the moment I saw pics sent to me from the customer.

Purely by the numbers the model was OK.... however, the customer had ordered the model is WSF-Polished, and the engine pods broke off during polishing. I had designed the supports for the engines with well over the amount needed to print OK, and even to withstand the polishing process... but what I didn't take into account was the twisting forces experienced by polishing media was enough to torque the engines right off. This wasn't a case of having sufficient wall thickness - it was a case of the design in 3D looking perfectly OK on screen, but real-world forces proving otherwise.

I was (hopefully) able to correct the problem by adding 2 more supports farther off the center axis. This should stop that part from rotating and thus from being twisted off.

I bring this case up specifically because, if the failure had been reported to me in the standard Shapeways blue-model-red-circle "might break" minimal communications failure email, I'd never have figured out what the issue was.
I still have not been notified by shapeways of that failure, however. I did update the model a few minutes after the customer contacted me and he sent me a follow-up message later telling me it was being re-printed for him, so we'll see soon if the revised model is the one they are printing, or if they are reprinting the older version.

I think you've hit the nail on the head Bathsheba.
After many successful prints of my Small Twin Rail Mobius in Silver without any reported problems, it has now been decided that the model is too fragile. Whilst I must accept this, the timing sucks for those who've ordered the model as a Christmas present as it is now too late to adjust the model for it to be re-ordered.

Yes, that's the phenomenon I have in mind. It bites you exactly at the moment when the model starts to get popular and you have a bunch of orders on deadline, because before that moment there wasn't a problem.

What's needed is to handle this in a way that doesn't blame or shame the people doing the printing. They're on our side...when they push the envelope and succeed with an iffy design, do we write back and say "Hey, awesome print!!"? We do not.

If we get angry when they try and it doesn't work out, they'll get defensive and start pushing back with more restrictive rules, rejecting models preemptively rather than taking risks near the edge of what the machines can do. I feel like that's not the outcome we're looking for.

If a design is decided as being iffy but falls within the scope of the material design guidelines and gives the production guys grief then surely (as Bill said before) the simplest solution is for the production guys to share their findings at the earliest opportunity so that everyone can move forward and be happy. With the small mobius pendant, it would take me mere minutes to adjust and upload if I was informed of a suitable wire thickness that would guarantee a successful print first time every time. As it stands the wire for that pendant is 1.30mm (+/- 0.02mm) thick and the Silver guidelines ask for 1mm as a 'free wire', so as anyone would, I thought I had covered the bases by making the wire 30% over the minimum.

Silver models that were successfully printed in the past have been rejected. It is embarrassing to have models that I have for sale be rejected, especially after I have test printed the models so they wouldn't be rejected. It reflects badly on my shop as well as on Shapeways.

I have responded (rather emphatically) to customer service. My hope is that they quickly rectify the situation and fulfill the order(s) without having the customer go through hoops to get their prints.

I know that this is an old story, but every time it happens, it gets me kind of fired up, and I apologize for the rant, and I apologize to the customers who placed orders. If there were problems with printing the initial prints, I was not made aware of them.

Exactly Paul, what we need from Shapeways is an open feedback channel that is available to the printers whether or not the model is printed.

Meanwhile I'll say it again: as users we've got to keep our good faith that the printers are doing their best even when things turn out inconvenient. 3D printing, like every other way of making things ever discovered, is a black art. There's no simple set of guidelines that will always predict exactly whether a model is printable. We make mistakes about what the machines can do, and so do the machine operators, and that's life on the cutting edge: we're doing science together.

If we start blaming them for trying and failing at the edge cases, they'll stop trying, and that would be sad.

The FUD guidelines state:How to design thin, unsupported walls
This pictures shows models made 0.6mm thick sheets (top), and 0.3mm thick sheets (bottom). You can see both models started to warp once the walls get big enough. Based on these tests, we conclude that for models in the 0.3-0.6mm wall thickness range, to keep free standing walls under 30x30mm. For walls of 0.6mm thickness, try to keep your free standing walls under 50x50mm.

Now the rejection image shows the walls are 0.4 to 0.5mm thick and only 1 or 2mm high!! well within the 30mmx30mm range.

This is the key question. Rejection emails are too often extremely difficult to understand. While a picture is said to be worth a thousand words, a few actual words along with it would be a lot more helpful.

This thread mentioned (or introduced ??)
another rule - "for stability, details have to be as wide as they are tall". (Also in the context of unexpected rejection of a proven
model). Maybe you got bitten by the same head of that multi-headed monster that dwells in the caverns underneath the printer floor
at shapeways ?

Unfortunately I can't promise you that the model in order 179276 is going
to be printed.
This is something which is being checked by our Production Facility and
they will make the call if the model can be printed or not.
Sorry that I can't help you further with this.
Kindly,
Christel
Happy Holidays!
Kind Regards,
Mrs. Christel Hagens
Customer Service Agent
www.Shapeways.com
===============================
Link to model: http://www.shapeways.com/model/654487

Here is the model printed a few weeks ago, about 12cm long and 2cm wide

Each time you upload, a new "Version #" is assigned (internally) to the model.
The external model# does not change, and the file name is whatever you uploaded.
The older versions of the model are kept.

Part of the reason for this is so that if you upload a model and order it, then change the model before it gets printed, you will get what you paid for: the first version (no changes allowed during the order stream).

If you upload any new version of a model, even if it is the same exact file as the previous time, that Version# is increased, and is then treated as though it has not been printed before. This is by design.. their system can't be sure whether you changed the model or not.

I have received in the past emails from Production "this model is particularly troublesome", but I will cut Shapeways some slack.. developing a method for that to be done on a consistent basis by 3rd party production teams (that may not speak my native language) is difficult. I don't know the specifics of how the files are transferred to the 3rd party. Imagine if they were sent over by CD.. there's no place to send messages (back)

Patience, Persistance, Politeness - the 3Ps will help us get us to Perfect Printed Products <grin>

Patience, Persistance, Politeness - the 3Ps will help us get us to Perfect Printed Products